Columns carry loads from beams and floors down to the foundations, and piers support decks and porches. Whether you pour into Sonotubes or timber forms, the concrete volume is the cross-section area times the height. Remember to include the part below ground.
How to use the Concrete Column Calculator
- Column shape
- Diameter / side a
- Side b
- Height
- Number of columns
- Waste
- Premix bag size
- Price per bag
- Ready-mix price
- Every result field is editable: type into Total concrete and Height plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose the column shape, enter its dimensions, height and number of columns, waste, bag size and prices. The calculator computes the volume of one column, the total with waste, bags of premix and the cost.
Premixed bag yields
| Bag | Yield | Bags per yd³ |
|---|---|---|
| 40 lb | 0.30 ft³ | 90 |
| 50 lb | 0.375 ft³ | 72 |
| 60 lb | 0.45 ft³ | 60 |
| 80 lb | 0.60 ft³ | 45 |
| 25 kg | ≈ 0.0117 m³ | ≈ 85 per m³ |
Tips for an accurate estimate
- Measure the formwork, not the drawing – forms bulge and subgrades are rarely perfectly flat, so add 5–10%.
- Below about 1 cubic yard, premixed bags are usually cheaper; above that, ready-mix saves time and gives a more consistent pour.
- Order ready-mix in quarter- or half-yard steps and ask about short-load fees for small deliveries.
- Keep fresh concrete damp for at least a week – curing matters as much as the mix for final strength.
Common mistakes to avoid
- Running short mid-pour, which leaves a weak cold joint.
- Adding extra water on site to make concrete easier to place – it lowers strength and increases cracking.
- Ignoring the volume of rebar, posts or pipes in the pour, or the gravel base under it.
Inputs explained
| Field | What to enter |
|---|---|
| Column shape | Choose one: Round, Square, Rectangular |
| Diameter / side a | Units: in, cm, mm, ft, m |
| Side b | Units: in, cm, mm, ft, m |
| Height | Units: ft, m, in, yd, cm |
| Number of columns | A number |
| Waste | In % |
| Premix bag size | Choose one: 40 lb bag (0.30 ft³), 50 lb bag (0.375 ft³), 60 lb bag (0.45 ft³), 80 lb bag (0.60 ft³) … |
| Price per bag | Units: /piece |
| Ready-mix price | Units: /yd³, /m³, /ft³ |
What each result means
- Total concrete = [Volume of one column]×[Number of columns]×(1 + [Waste]÷100)
- Weight = [Total concrete]×2400
- Premix bags = ceil([Total concrete]÷[Premix bag size])
- Cost with bags = [Premix bags]×[Price per bag]
- Cost with ready-mix = [Total concrete]×[Ready-mix price]
Formula
Round: V = π/4 × D² × HSquare: V = a² × H; Rectangular: V = a × b × HTotal = V × columns × (1 + waste)Worked example
Inputs — Column shape: Round; Diameter / side a: 12 in; Side b: 16 in; Height: 10 ft; Number of columns: 4; Waste: 7 %; Premix bag size: 80 lb bag (0.60 ft³); Price per bag: $6.5 /piece; Ready-mix price: $150 /yd³.
Results — Volume of one column = 7.854 ft³; Total concrete = 1.245 yd³; Weight = 5,036 lb; Premix bags = 57; Cost with bags = $370.50; Cost with ready-mix = $186.75.
Frequently asked questions
How much concrete is in a 12 in round column 10 ft tall?
7.85 ft³ (0.29 yd³) – about 13 bags of 80 lb premix.
How do I calculate a square column?
Side × side × height; a 12 × 12 in column 10 ft high is 10 ft³.
Do I need rebar in a column?
Structural columns need vertical bars and ties designed by an engineer; deck piers often need only a single bar or none.
What formula does the Concrete Column Calculator use?
Round: V = π/4 × D² × H.